Cast articulated tool

ABSTRACT

An articulated cutting tool, such as scissors, is formed by casting a first element with a pivot region, and casting a second element using the pivot region of the first element as the mold for the pivot region of the second element. The pivot regions of the elements are tapered, and in order to free the pivot joint, the pin is upset, for example by punching in the axial direction of the pin. The articulated element thus formed is coated with a hard coating material, and the cutting edges of the tool are ground to provide a sharp cutting edge for shearing action to which the layer of hard coating material extends. The invention is also adaptable to articulated tools, such as pliers, which do not have cutting edges, in which case the plating and grinding of the tool may be omitted.

This is a division of application Ser. No. 536,357, filed Dec. 26, 1974,now U.S. Pat. No. 3,965,779 which in turn is a divisional of U.S. Ser.No. 434,106, filed Jan. 17, 1974, now U.S. Pat. No. 3,880,021.

This invention relates to hinged articles, such as scissors pliers,forceps, nippers and the like, and is more particularly directed to sucharticles and the production of such articles wherein the hinged elementsare sequentially cast and the first cast member is formed with a pivotthat serves as a mold for the casting of the hinge portion of the othermember. This casting technique is hereinafter referred to as"intercasting".

In one method of intercasting, such as disclosed in U.S. Pat. No.2,577,350, L. H. Morin, for example, for the production of hinges andthe like, one of the members of the article is first cast in a mold,this member being provided with a pivot pin or aperture during thecasting process. The other member of the article is then cast in a mold,with the first member forming the part of the mold defining the joint ofthe article. In this process, it is thereby unnecessary to provide aseparate hinge pin or screw for holding the members together and formingthe pivot thereof, and the process constitutes a relatively inexpensivetechnique for forming an articulated product.

While the above described process has been successfully employed in theproduction of many useful articles, such as hinges, its adaptation tothe production of cutting and holding tools, such as scissors andpliers, has been limited for several reasons. Thus, while for a numberof years novelty items in the form of scissors and pliers have beenproduced by this technique, they have been more in the nature of toy ornovelty items, since their operating characteristics were notsatisfactory for normal use of such items. For example, due to theparticular process as above described employed in the formation of thejoint itself, there tended to be binding between the articles, so thatthe normal free action expected in tools of this type was not provided.Further, particularly with respect to cutting tools such as scissors,the cutting edges were not satisfactory for any practical cuttingoperations. One reason for the practicality of such scissors resides inthe fact that the metals from which the articles must be molded does notenable the provision of 2 sharp long lasting cutting edge. Thus,articulated tools formed by the above casting process were notconsidered to be generally practical or useful tools.

In some fields of use, for example in medical operations, it isnecessary to employ reliable articulated cutting instruments such asshears, that will maintain their cutting edges without questionthroughout their desired period of use, and that have the necessaryfreedom of action wthout binding to insure accurate control of the tool.Such tools are relatively expensive. It has been found that, for examplein hospitals where stocks of high quality scissors must be maintained,it is difficult to keep track of such items, and that they must becontinually replaced, possibly due to the attraction that such articleshave for the personnel employing them or the personnel to whom they areavailable. While each such tool of course is not overly expensive fromthe standpoint of the operation of the hospital itself, the need forconstantly replacing the items presents a constant budgetary problem forthe institution. Up to now, a satisfactory inexpensive articulatedcutting tool of sufficient quality and reliability for use in hospitalshas not been available.

It is therefore the object of this invention to provide an inexpensivearticulated cutting or holding tool, as well as an apparatus forproducing such a tool, in order to overcome the above discusseddisadvantages of prior cutting and holding tools.

In accordance with one aspect of the invention, an articulated tool, forexample a cutting tool such as scissors, is formed by intercasting theseparate scissor elements. The pivot of the scissor elements is castwith a tapered shape. In order to provide freedom of movement betweenthe elements, the pivot of the scissors is upset, for example bypunching, thereby providing a small spacing between the elements toenable free relative movement. The elements, at least in the regions oftheir cutting blades, are plated with a hard material, such as nickel orchromium. In order to ensure a sharp cutting edge for the scissors, thecutting edges are ground in the conventional manner. While this grindingmay remove all of the hard coating material in one region of the scissorblades, the hard coating material does extend to that region so that thehard coating material is present in the regions of the scissors wherethe shearing action actually occurs.

The scissors thus made are inexpensive to produce, provide the desirablefreedom of movement at the pivot joints, and are reliable. In view ofthe minimum expense involved in the production of the scissors, they maybe considered as expendable items.

The method of the invention is also adaptable to other articulatedcutting tools, as well as to articulated non-cutting tools such aspliers and the like, in which case the plating and grinding steps may ifdesired be omitted.

In accordance with a further aspect of the invention, an articulatedtool is provided in which the pivot pin for the articulated elements isintegrally formed with one of the elements, the pivot pin being taperedand having an enlarged head to hold the second element at the pivotjoint. The pin may have a groove extending therein from the head, thegroove preferably being circular, to facilitate upsetting of the pivotpin for providing freedom of relative movement of the articulatedelements.

If the articulated tool is a cutting tool, such as scissors, the tool isformed of a soft material, such as a casting material, and provided witha hard outer coating of a material such as nickel or chromium. Thecutting edge of the tool is ground to a sharp edge, with the hardcoating material extending to the cutting edge itself but the castingmaterial extending to the ground face.

In articulated cutting tools such as scissors, it is conventional thatthe cutting blades be slightly bent in order to ensure proper shearingaction between the blades. In accordance with a further aspect of theinvention, a tool is provided for facilitating the bending of a blade ofa pair of scissors. The tool is comprised of an anvil having a channeltherein for receiving one element of the scissors, whereby the otherarticulated element of the scissors may rest on the tops of the sides ofthe channel. The tool further comprises a punch for punching the pivotof the scissors to upset the pivot joint, thereby providing freedom ofmovement at the pivot joint. The tool is especially adaptable for thefreeing of the pivot joint of intercast scissors having tapered pivotregions in accordance with the invention.

In order that the invention will be more clearly understood, it will nowbe described in greater detail with reference to the accompanyingdrawings, in which:

FIG. 1 is a plan view of a pair of scissors, which may be formed inaccordance with the present invention;

FIG. 2 is a cross sectional view of the pivot region of a pair ofscissors, illustrating a prior art intercasting technique;

FIG. 3 is a cross sectional view of the pivot joint of an articulatedtool in accordance with the invention;

FIG. 4 is a cross sectional view corresponding to the view of FIG. 3 andillustrating a technique for upsetting the pivot joint;

FIG. 5 is a cross sectional view of a modification of the pivot joint ofFIG. 3;

FIG. 6 is a top view of the pivot joint of an articulated tool inaccordance with FIG. 5;

FIG. 7 is a cross sectional view illustrating the upsetting of the pivotjoint of the arrangement of FIG. 5;

FIG. 8 is a top view of an upsetting tool, in accordance with theinvention, and partially illustrating a pair of scissors mounted forupsetting of the pivot therein in accordance with the invention;

FIG. 9 is a cross sectional view of the tool and scissors of FIG. 8, andfurther illustrating upsetting and blade bending tools in combinationtherewith;

FIG. 10 is a flow diagram for the method of forming an articulatedcutting tool in accordance with the invention;

FIG. 11 is a cross sectional view of the scissors of FIG. 1, taken alongthe lines 11--11, and illustrating the core of casting material and thecoating of hard material on the scissor blades;

FIG. 12 is a cross section of scissor blades corresponding to the viewof FIG. 11, with the cutting edges ground off; and

FIG. 13 is a plan view of a pair of pliers which may be formed inaccordance with the invention, and have an articulated joint inaccordance therewith.

Referring now to the drawings, and more in particular to FIG. 1, thereinis illustrated a typical pair of scissors, which may be employed, forexample, as a surgical instrument. It will be understood of course, thatthe present invention is not limited to the provision of scissors forthis particular use, nor is it limited to cutting tools, since it isalso applicable to other articulated tools such as pliers and forcepsand the like. The scissors of FIG. 1 have the general conventionalconfiguration with a pair of blades 20 and 21 hinged together at a pivot22. The blades 20 and 21 have cooperating cutting edges 23 and 24respectively on one end, and looped handles 25 and 26 respectively onthe other ends thereof with respect to the pivot 22. For some purposes,such as for cutting threads, sutures, or the like, one of the blades maybe provided with a notch 27 near the end of the respective cutting edge,in conventional fashion.

While the scissors of FIG. 1 may be formed by a number of differentprocesses, the present invention is directed to the formation of thearticle by the intercast process. In this process, as described anddisclosed, for example, in U.S. Pat. No. 2,577,350, one of the scissorblades is first cast, for example, with a pivot pin being moldedintegrally therewith. When the second scissor blade is subsequentlycast, the pivot pin of the first cast blade forms part of the moldthereof, whereby the articulated joint is formed during the castingprocess and not by the later insertion of a pivot member such as a pinor screw or the like.

In the above paragraphs it was noted that scissors have been produced inthe past employing the intercast technique. The form of the articulatedjoint of such known devices is illustrated in FIG. 2. This illustrationis a cross sectional view taken along the lines 2--2 of the scissors ofFIG. 1, when such scissors have been formed by prior art intercasttechniques. As illustrated in FIG. 2, one of the scissor blades 20 hasintegrally cast therewith a pivot pin 30 extending normal to the axis ofthe blade. The pin 30 is provided with an enlarged head 31 which extendsradially beyond the central portion of the pin. The other blade member21 is cast with the pin 30 forming a part of the mold, thereby formingthe articulated joint between the members without the necessity ofproviding a separate pivot pin or screw, the enlarged head 31 of the pin30 insuring that the blade elements do not become separated. A simulatedscrew head 32 has generally been provided on the other side of the blade21 aligned with the pin 30 for the sake of appearance, since it isnormally expected that scissors should have some constructive feature atthis point. It is to be further noted that in the scissors of FIG. 2,the pin 30 has an equal diameter throughout its length.

A pair of scissors formed in accordance with FIG. 2 is generally subjectto binding and uneven operation. This may be a result of the fact thatthe pivot pin 30 cannot be perfectly formed to provide a perfectlycircular pin with very smooth surfaces, whereby any non-uniformities inits shape or in its surface will tend to create binding at the pivotjoint. As a consequence, scissors provided with a joint such asillustrated in FIG. 2 tend to have a binding uneven action at leastuntil the metal at the pivot has become worn by use.

According to the invention, in order to overcome this problem, asillustrated in FIG. 3, the scissors blade 20' is provided with a pin 30'cast integrally therewith that has a taper. The end of the centralportion of the pin 30' away from the blade 20' is of smaller diameterthan the end thereof toward the blade 20'. The pin 30' is also providedwith an enlarged head 31', as in the arrangement of FIG. 2. The otherblade member 21' is cast with the pin 30' forming a part of the mold, ina similar manner to that above described with respect to FIG. 2.Following the formation of the articulated joint as illustrated in FIG.3, the pin 30' is upset to free the joint for smooth action. Thisoperation, which will be discussed in greater detail in the followingparagraphs, consists essentially of restraining the blade 21' frommovement, for example by providing supports at the points indicated bythe arrows 35 in FIG. 4, and then striking the end of the head 31' witha punch, for example, punch 36, in the direction indicated by the arrow37. This operation effects the deformation of the pin 30' and its head31', so that the blade 20' is forced downwardly slightly away from theblade 21', as illustrated in FIG. 4. As a result of this upsetting ofthe pin, it is to be noted that due to the provision of the taper on thepin 30', a small clearance 38 is provided between the pin 30' and themating recess 39 of the blade 21'. A small clearance 40 also appearsbetween the blades 20' and 21'.

The clearances around the pin and between the blades sufficiently freethe articulated joint, so that free and steady movement between thescissor blades is obtained. For example, the clearance 40 may be about0.001 inches.

The angle of the taper of the pin 30' is not particularly critical,although it should be great enough that only a small degree of upsettingof the pin is adequate to free the pivot joint while not being too greatthat the strength of the pin is weakened at one end. For example, it ispreferred that the taper angle of the pin, with respect to its axis, beabout 5° .

The scissors formed in accordance with the invention may be formed ofany conventional casting material, such as for example, Beric, a zinccasting alloy. It is preferred that the casting material have more than50% zinc, with the other constituents thereof being aluminum, copperand/or magnesium.

A modification of the intercast joint of FIG. 3 is illustrated in FIGS.5 and 6, with FIG. 5 representing a cross sectional view as in FIG. 3,and FIG. 6 representing a plan view of the top of the pivot region ofthe scissors. The intercast elements illustrated in FIGS. 5 and 6 areidentical to those of FIG. 3, with the exception that a groove 45 isprovided extending axially into the pin 30' from the head 31' thereof.The groove, as illustrated in FIG. 6, may be circular.

As illustrated in FIG. 7, when the intercast joint of FIGS. 5 and 6 isupset in a manner similar to that illustrated in FIG. 4, thecircumferential regions 46 of the enlarged head 31' are forced into thegroove 45. In other words, the downward forces exerted by the punch 36tend to force the circumferential regions 46 of the head downwardagainst the top of the member 21'. Since the groove 45 permits radialinward displacement of the circumferential regions of the head 31', thecircumferential regions 46 effectively pivot about the edges of theaperture in the scissor member 21' to be deformed into the groove 45.The radial inward relief of the deformation provided by the groove 45thus permits upsetting of the head 31' of the pin with considerably lessforce than that required in the arrangement of FIG. 3. As a consequence,the upsetting of the arrangement of FIGS. 5 and 6 is effected with lessdanger of undesirable bending of the scissor members 20' and 21'. Thiscan be of importance, since the scissors are cast of a relatively softmaterial.

FIGS. 8 and 9 illustrate in greater detail a preferred technique forupsetting the pin of the scissors. As illustrated in these figures, ananvil 50 is provided having a channel 51 in its upper surface. The sides52 and 53 of the channel are separated by a distance slightly greaterthan the width of a scissor blade in the region of the pivot joint. Inorder to upset the pin of an intercast scissors, the scissor blades areslightly opened as illustrated in FIG. 8, and the scissor member 20'having the pin cast integrally therewith is fitted in the channel 51 toextend generally longitudinally therein. The undersurfaces of thescissor member 21' thus rest on the side members 52 and 53 of thechannel, this scissor member extending at an angle to the longitudinaldirection of the anvil.

As illustrated in FIG. 9, with the scissor members thus supported, thepunch 36 is forced downwardly onto the head 31' to effect the upsettingas illustrated in FIGS. 4 and 7. In other words, since the scissormember 21' is supported on the side members 52 and 53 from downwardmovement, the punching of the top of the pin 30' effects the distortionand upsetting of the head of the pin.

In order to ensure a positive shearing action with the blades of thescissors in use, it may be necessary to slightly bow the blades 20' and21' inwardly, i.e., toward each other. Otherwise, the blades may besufficiently separated that reasonable shearing action is not obtained.This inward bowing of the blades may be obtained by casting the bladesin the desired shape in the intercast process. Alternatively, however,one or both of the blades may be bent following the intercastingprocess. Thus, as illustrated in FIG. 9, with the blade 21' resting onthe anvil, a suitable punching tool 55 may be forced downwardly, in thedirection of the arrow 56, to bend the blade of the scissor member to adesired extent, for example as illustrated in dash lines in FIG. 9.

A method for forming the scissors in accordance with the invention isillustrated in the flow diagram of FIG. 10. In the first step of thisprocess, the scissor elements are intercast, as above described. Thenthe pivot is upset, for example as illustrated in FIGS. 4 and 7 with atool which may be of the form illustrated in FIGS. 8 and 9. If theblades of the scissors have not been cast with the desired bendstherein, one or both of the blades may be bent at this time, asillustrated in FIG. 9.

The thus formed scissors are then deburred according to conventionalpractice, for example by tumbling, in order to remove undesirableprojections and burrs formed therein during the casting process.

The thus formed scissors have the desired freedom of movement at thepivot pin, so that no undesirable binding or sticking of the joint ispresent. The scissors are also bent to the desired extent for effectiveshearing action at the blades. As discussed above, the scissors havebeen cast from a conventional casting material, which may be relativelysoft so that the scissors do not form a practical cutting tool. Thus,the cutting edges would be dulled by only minor cutting operations.

In accordance with the invention, in order to overcome this problem, inthe next step of the method illustrated in FIG. 10 the scissors areplated with a suitably hard material such as nickel or chromium. Thisplating may be effected by any conventional plating technique, such asbarrel plating or rack plating. While it is only necessary, in theory,that the edges of the blades be so plated to provide a hard material inthe shearing regions, if desired the entire scissors thus formed may beplated. For example, the plating of the entire scissors provides theadvantage that the scissors may be more effectively cleaned andsterilized and the soft material of the interior of the scissors willnot be as subject to abrasion and nicking.

Although the blades of the scissors, following the plating thereof witha hard material, now have sufficient hardness that they would be capableof use for a reasonable period of time without dulling, the edgesproduced by conventional plating techniques are not sharp. For example,following the plating step, the edges of the blades of the scissors maybe troubled with radiuses of, for example, 0.004 to 0.005 inches. Thesectional view of the blades after the plating step is illustrated inFIG. 11, this figure being a cross sectional view of the scissors ofFIG. 1 taken along the line 11-11, with a scissors formed in accordancewith the invention. As illustrated in this figure, the blades 20' and21' of casting material are coated with a layer 60 of hard material suchas nickel or chromium. The shearing edges 61 of the blades are rounded,however, due to the plating as above described, and possibly also due toa certain extent to the difficulties of casting an extremely sharp edge.The scissors having a rounded edge, as illustrated in FIG. 11, are notsuitable for precise cutting operations.

Further, in accordance with the invention, in order to provide ascissors with sharp cutting edges, the edges of the blades are ground asillustrated in FIG. 12. The angle of grinding of the edges is inaccordance with the general procedure in the grinding of edges ofscissors. It is to be noted, however, that the hard coating layer 60 maybe entirely ground off in this grinding step, so that the base castingmaterial is exposed at the surfaces 70 and 71. Thus, since the layer 60may be plated on the scissors with a thickness of, for example, from0.001 inch to 0.0015 inches, the necessary grinding of the cutting edgesof the scissors to provide sharp edges may entirely remove the hardmaterial at the faces 70 and 71. In accordance with the invention,however, this does not detract from the utility of the scissors. Thegrinding of the cutting edges of the scissors has now providedadequately sharp cutting edges for effective shearing action. Since thelayer 60 on each of the blades extends to the faces 70 and 71, the hardmaterial of layer 60 is present in the region where the shearing actionof the scissors actually occurs, i.e., at the edges 72 and 73.Consequently, the scissors may be employed effectively as a cuttingtool. While the scissors will of course not have the longer life ofconventional scissors, they are quite suitable for precise cutting forlimited periods of time for some applications.

The scissors formed as above described, in accordance with theinvention, are very economical, since the intercasting process minimizesexpenditures necessary in forming the basic structure. The desired freeaction of the scissors is readily and economically effected by theupsetting of the pivot pin as above discussed. A minimum amount ofexpensive material is employed in the formation of the hard layer 60, sothat the material cost of the scissors is also very low. Consequently,the scissors formed in accordance with the invention as above describedmay be considered as throw-away items. This is an especial advantage inthe medical field, since the scissors may be employed for a singleoperation and then disposed of or recycled. The resultant cost of suchthrow-away items, for example in hospitals, is considerably less thanwhen conventional expensive and precise scissors are employed, and thereis no necessity to keep track of the items since they are completelyexpendable. In addition to being inexpensive, the scissors are ofsufficient quality and reliability for use in medical procedures.

While the invention has been particularly described with reference toscissors as cutting tools, it is obvious that the invention may also beemployed for other cutting instruments, such as pliers, forceps, nippersand the like. In addition, certain aspects of the invention areadaptable for non-cutting articulated tools, such as pliers, asillustrated in FIG. 13, and the like. For example, in the formation of apair of pliers as illustrated in FIG. 13, the elements of the pliers areintercast as illustrated in FIG. 3, with the tapered interconnectingpin. In order to provide adequately free action of the pliers, the pinsof the pliers are upset, for example as illustrated in FIGS. 4 and 7.The pliers then may be deburred according to conventional practice. Ifdesired, in order to provide a hard surface on the pliers to extendtheir useability to some extent, the pliers may be coated byconventional techniques with a harder material such as nickel orchromium. It is of course not necessary to grind any cutting edges inpliers of this type, so that the last above described step in theproduction of scissors and other cutting tools may be omitted.Consequently, the invention is adaptable to articulated cutting tools aswell as to articulated holding tools incorporating a pair of jaws. Theholding tools formed in accordance with the invention may also beexpendable if desired.

It is also contemplated in accordance with the invention, that certainaspects thereof are advantageous with respect to non-articulated tools.For example, non-articulated shearing tools may have blades formed inaccordance with the invention, by casting or otherwise forming a blademember of a soft material then coating the soft material with a hardmaterial by conventional techniques, and subsequently grinding off acutting edge of the shearing tool to form a cutting edge with the layerof the hard material extending to the cutting edge. The soft material inthis case may be a casting material such as zinc casting material, andthe coating material may, as above described, be a material such asnickel or chromium.

While the invention has been disclosed and described with reference to alimited number of embodiments, it will be apparent that manymodifications and variations thereof are possible, and it is intended inthe following claims to cover each such variation and modification asfalls within the true scope of the invention.

What is claimed is:
 1. A cast articulated shearing tool comprising firstand second cast members each having a shearing blade on one end thereof,said first member having a tapered aperture extending therethroughspaced from the respective blade, said second member having a pin withan enlarged head extending from one side thereof spaced from therespective blade and being integral with said second member, said pinbeing tapered with its larger diameter end toward said second member,the tapered portion of said pin corresponding in form to the form ofsaid aperture and being fitted therein to form an articulated jointbetween said members for holding said blades in relative shearingrelationship.
 2. The shearing tool of claim 1 wherein said members areformed of a die casting metal with an exterior coating of a metal harderthan said die casting metal.
 3. The shearing tool of claim 2 whereinsaid die casting metal is a zinc base casting metal, and said hardermetal is a metal selected from the group consisting of nickel andchromium.
 4. The shearing tool of claim 2 wherein said blades have firstsubstantially parallel faces normal to the axis of said joint, andsecond faces extending at an angle to said first faces, whereby theedges of said blades between the respective first and second races formshearing edges.
 5. The shearing tool of claim 4 wherein said castingmetal extends to the surface of said second faces and said first facesare coated with said harder metal, whereby said harder metal extends tosaid shearing edges.
 6. In an intercast shearing tool having first andsecond members with shearing blades and being formed of a die castingmetal, the members being joined at a pivot axis by a pin cast integrallywith the first member and fitted into a correspondingly shaped aperturein the second member, the pin having an enlarged head to hold saidmembers together, the improvement wherein said pin and aperture havematching tapered portions, with the larger diameter end of the taperedportion of said pin being toward said first member.
 7. The shearing toolof claim 6 wherein said blades have first substantially parallel facesnormal to said pivot axis, and second faces extending at an angle tosaid first faces, whereby the edges of said blades between therespective first and second faces extending to the surface of saidsecond faces, and wherein said first faces are coated with a metalharder than said die casting metal and extending to said shearing edges.